Summer of Desperate Races — Angela Dorsey

On the same day that Evy learns another of her mom's secrets, she also discovers that they are almost out of money! And her mom has stopped painting, so there will be no more money coming in. How will they live? Wanting to help, Evy enters a dangerous local race, hoping to win the prize money. However, the Downhill Mountain Race isn't the most important race Evy and Rusty will run - or the most perilous. At risk, not prize money, but innocent mustangs who have been forced from their wild homes. Can Evy save them?